Synthesis of core–shell N-TiO2@CuOx with enhanced visible light photocatalytic performance

In this paper, a core–shell N-TiO₂@CuO_x nanomaterial with increased visible light photocatalytic activity was successfully synthesized using a simple method. By synthesizing ammonium titanyl oxalate as a precursor, N-doped TiO₂ can be prepared, then the core–shell structure of N-TiO₂@CuO_x with a catalyst loading of Cu on its surface was prepared using a precipitation method. It was characterized in detail using XRD, TEM, BET, XPS and H₂-TPR, while its photocatalytic activity was evaluated using the probe reaction of the degradation of methyl orange. We found that the core–shell N-TiO₂@CuO_x nanomaterial can lessen the TiO₂ energy band-gap width due to the N-doping, as well as remarkably improving the photo-degradation activity due to a certain loading of Cu on the surfaces of N-TiO₂ supports. Therefore, a preparation method for a novel N, Cu co-doped TiO₂ photocatalyst with a core–shell structure and efficient photocatalytic performance has been provided.

In this paper, a core–shell N-TiO₂@CuO_x nanomaterial with increased visible light photocatalytic activity was successfully synthesized using a simple method.     

Correction: Preparation and photocatalytic application of a S,Nd double doped nano-TiO2 photocatalyst

Correction for ‘Preparation and photocatalytic application of a S, Nd double doped nano-TiO₂ photocatalyst’ by Shuo Wang et al., RSC Adv., 2018, 8, 36745–36753.

In the published article, Liming Bai was incorrectly not listed as the corresponding author. The correct version is shown here.The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers.     

CdSe/ZIF-8-x: synthesis and photocatalytic CO2 reduction performance

The photocatalytic reduction of CO₂ is an effective way to solve the greenhouse effect. Different kinds of materials, such as semiconductors, coordination compounds, and bioenzymes, have been widely investigated to increase the efficiency of the photocatalytic reduction of CO₂. However, a high selectivity and great stability are still challenges for material scientists. Here, we report for the first time visible light photocatalytic CO₂ reduction by a series of CdSe/ZIF-8 nanocomposites combining the excellent CO₂ adsorption capacity of ZIF-8 and the narrow energy gap of CdSe quantum dots (QDs). The composites show a higher catalytic performance than those of the pure components. Among CdSe/ZIF-8-x (x = n_CdSe/n_ZIF-8), the highest yield (42.317 μmol g⁻¹) for reducing CO₂ to CO in 12 h, was obtained using nanocomposites with a ratio of 0.42 (n_CdSe/n_ZIF-8) within the range of investigation.

CdSe/ZIF-8-x combines the excellent CO₂ adsorption capacity of ZIF-8 and the narrow energy gap of CdSe to show an enhanced CO₂ photoreduction performance.

Nowadays, global energy shortage and environmental pollution are two major obstacles to the development of human society, and have attracted increasing concern. Using solar energy to convert CO₂ into valuable fuels or chemicals is extremely attractive due to its dual function of the reduction of the greenhouse effect and also as an alternative energy source to fossil fuels. Recently, different kinds of materials, such as semiconductor materials,^1–3 metal complexes,^4–6 and bioenzyme catalysts,⁷ have been explored for photocatalytic CO₂ reduction.Metal–organic frameworks (MOFs) constructed from metal-containing clusters and organic building blocks are types of crystalline porous materials, and have been widely applied in many fields, such as gas storage,⁸ electrochemical energy storage (EES)^9,10 and catalysis.¹¹ Recently, MOFs^12–14 have been considered as potential new catalysts due to their excellent capability for CO₂ adsorption and capture.¹⁵ These porous materials provide a large number of catalytic active sites, and their porous structures are conducive to charge transfer.¹⁶ During the adsorption process, CO₂ coordinates with unsaturated metal sites and forms chemical bonds with MOFs.¹² Blom and co-workers demonstrated that CO₂ can interact with metal ions and form end-on adducts with one of the oxygen lone pair orbitals.¹⁷ZIF-8, which is constructed from Zn²⁺ centres and imidazolate ligands, shows a high CO₂ adsorption capacity since the imidazolate ligand has a high adsorption capacity for CO₂ and also a strong complexation ability of CO₂.¹⁸ However, ZIF-8 has a wide band gap (4.9 eV, ref. 19), which means that ZIF-8 is barely photoactive enough to catalyse CO₂ reduction. However, CdSe QDs can easily be excited to generate electron–hole pairs upon visible light irradiation due to their narrow band gap. Osterloh and co-workers reported CdSe QDs of several sizes applied to photocatalytic H₂ evolution and showed the quantitative relationship between the degree of quantum confinement and the photocatalytic H₂ evolution.²⁰In this work, we synthesized a series of CdSe/ZIF-8-x composites, which combine the excellent CO₂ adsorption capacity of ZIF-8 with the narrow energy gap of CdSe QDs. X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS) indicated the successful combination of CdSe QDs and ZIF-8. The CdSe/ZIF-8 composite exhibits an increased yield for reducing CO₂ to CO compared with pure CdSe QDs or ZIF-8. Under visible light irradiation for 12 h, the CO yield was 42.317 μmol g⁻¹, which is 6.13 and 10.84 times the yields catalysed by CdSe (6.901 μmol g⁻¹) and by ZIF-8 (3.905 μmol g⁻¹), respectively.Reagents used in this work were analytically pure and used without further purification. Powder X-ray diffraction (PXRD) analysis was performed using a Rigaku Dmax-2000 diffractometer equipped with a Cu Kα (λ = 0.15406 nm) radiation source. The morphology of the catalysts was observed by transmission electron microscopy (TEM, JEOL JEM-2100F) operated at 200 kV. Scanning electron microscopy (SEM) pictures were prepared using a Hitachi scanning electron microscope S-4800. Elemental mapping was carried out by energy dispersive X-ray spectroscopy (EDS) on the same instrument. Inductively coupled plasma spectrometry (ICP, Cary5000) was used for multi-elemental analyses. The CO₂ absorption behaviours of the catalysts were studied with physical adsorption apparatus (ASAP 2020M). Solid UV-visible diffuse reflectance spectroscopy (UV-vis DRS) was carried out at room temperature to evaluate the band gap energy (E_g). The products of the photocatalytic CO₂ reduction were detected by gas chromatography (GC7900, Techcomp). Dynamic light scattering (DLS) measurements were carried out on an Elitesizer from Brookhaven.CdSe QDs were synthesized by a previously reported procedure.²¹ The resulting CdSe QDs were precipitated by adding ethanol and dispersed in 5 mL of hexane as a stock solution.The synthesis of CdSe/ZIF-8 was based on the pure ZIF-8 synthesis process with modification.²² A certain quantity of the above CdSe QD stock solution was precipitated by adding ethanol, and re-dispersed in 5 mL of an n-hexanol solution of 0.1642 g (2 mmol) of 2-methylimidazole (Hmim) via ultrasonication. A solution of Zn(NO₃)₂·6H₂O (0.074 g, 0.25 mmol) in 5 mL of n-hexanol was rapidly poured into the above solution under stirring. The product was collected by centrifugation after 1 h, washed with n-hexanol twice and dried at 80 °C for 12 h under vacuum. The samples produced from n_Cd²⁺/n_Zn²⁺ equal to 0.4, 0.8, and 1.2 were named as samples 1 to 3, respectively.The photocatalytic CO₂ reduction performance of CdSe/ZIF-8-x was performed in a typical catalytic system with [Ru(bpy)₃]²⁺ (bpy = 2′,2-bipyridine) as a photosensitizer and triethanolamine (TEOA) as a sacrificial reducing agent in CO₂-saturated acetonitrile (MeCN).^23–27 The photosensitizer [Ru(bpy)₃]Cl₂·6H₂O (2 mg) and catalysts CdSe/ZIF-8-x (5 mg) were dispersed in a solution of 1 mL of triethanolamine (TEOA) and 4 mL of acetonitrile. Before irradiation, the suspension was purged with CO₂ for 15 min to eliminate any air. With vigorous stirring, a 300 W Xe lamp with a 420 nm cut-off filter was utilized as the light source. After illumination for 12 h, the produced gases were analysed and quantified by gas chromatography.The molar ratios of CdSe to ZIF-8 of the composites were characterized by ICP (

Correction: Expedient synthesis of eumelanin-inspired 5,6-dihydroxyindole-2-carboxylate ethyl ester derivatives

Correction for ‘Expedient synthesis of eumelanin-inspired 5,6-dihydroxyindole-2-carboxylate ethyl ester derivatives’ by Andrew H. Aebly et al., RSC Adv., 2018, 8, 28323–28328.

The authors regret that an incorrect grant number was shown in the acknowledgements section of the published article. The corrected section should read:We thank the National Science Foundation (RUI grant CHE-1305919) and Oberlin College for financial support.The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers.     

Correction: Nano zero valent iron (nZVI) particles for the removal of heavy metals (Cd2+, Cu2+ and Pb2+) from aqueous solutions

Correction for ‘Nano zero valent iron (nZVI) particles for the removal of heavy metals (Cd²⁺, Cu²⁺ and Pb²⁺) from aqueous solutions’ by Mekonnen Maschal Tarekegn et al., RSC Adv., 2021, 11, 18539–18551. DOI: 10.1039/D1RA01427G.

The authors regret that reference 48 was incorrect. The correct reference is given below as reference 1.¹The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers.     

One-pot synthesis of Cu2O/C@H-TiO2 nanocomposites with enhanced visible-light photocatalytic activity

As an environment-friendly semiconductor, titanium dioxide (TiO₂), which can effectively convert solar energy to chemical energy, is a crucial material in solar energy conversion research. However, it has several technical limitations for environment protection and energy industries, such as low photocatalytic efficiency and a narrow spectrum response. In this study, a unique mesoporous Cu₂O/C@H-TiO₂ nanocomposite is proposed to solve these issues. Polystyrene beads ((C₈H₈)_n, PS) are utilized as templates to prepare TiO₂ hollow microspheres. Cu₂O nanocomposites and amorphous carbon are deposited by a one-pot method on the surface of TiO₂ hollow spheres. After the heterojunction is formed between the two semiconductor materials, the difference in energy levels can effectively separate the photogenerated e⁻–h⁺ pairs, thereby greatly improving the photocatalytic efficiency. Furthermore, due to the visible band absorption of Cu₂O, the absorption range of the prepared nanocomposites is expanded to the whole solar spectrum. Amorphous carbon, as a Cu₂O reduction reaction concomitant product, can further improve the electron conduction characteristics between Cu₂O and TiO₂. The structure and chemical composition of the obtained nanocomposites are characterized by a series of techniques (such as SEM, EDS, TEM, XRD, FTIR, XPS, DRS, PL, MS etc.). The experimental results of the degradation of methylene blue (MB) aqueous solution demonstrate that the degradation efficiency of Cu₂O/C@H-TiO₂ nanocomposites is about 3 times as fast as that of pure TiO₂ hollow microspheres, and a more absolute degradation can be achieved. Herein, a recyclable photocatalyst with high degradation efficiency and a whole solar spectrum response is proposed and fabricated, and would find useful applications in environment protection, and optoelectronic devices.

As an environment-friendly semiconductor, titanium dioxide (TiO₂), which can effectively convert solar energy to chemical energy, is a crucial material in solar energy conversion research.     

A facile chemical synthesis of nanoflake NiS2 layers and their photocatalytic activity

A single-phase and crystalline NiS₂ nanoflake layer was produced by a facile and novel approach consisting of a two-step growth process. First, a Ni(OH)₂ layer was synthesized by a chemical bath deposition approach using a nickel precursor and ammonia as the starting solution. In a second step, the obtained Ni(OH)₂ layer was transformed into a NiS₂ layer by a sulfurization process at 450 °C for 1 h. The XRD analysis showed a single-phase NiS₂ layer with no additional peaks related to any secondary phases. Raman and X-ray photoelectron spectroscopy further confirmed the formation of a single-phase NiS₂ layer. SEM revealed that the NiS₂ layer consisted of overlapping nanoflakes. The optical bandgap of the NiS₂ layer was evaluated with the Kubelka–Munk function from the diffuse reflectance spectrum (DRS) and was estimated to be around 1.19 eV, making NiS₂ suitable for the photodegradation of organic pollutants under solar light. The NiS₂ nanoflake layer showed photocatalytic activity for the degradation of phenol under solar irradiation at natural pH 6. The NiS₂ nanoflake layer exhibited good solar light photocatalytic activity in the photodegradation of phenol as a model organic pollutant.

A single phase nanoflake NiS₂ layer synthesized by a facile chemical bath deposition showed good solar light photocatalytic degradation of phenol with good stability and reusability.     

Correction: Influence of Cu doping on the visible-light-induced photocatalytic activity of InVO4

Correction for ‘Influence of Cu doping on the visible-light-induced photocatalytic activity of InVO₄’ by Natda Wetchakun et al., RSC Adv., 2017, 7, 13911–13918, DOI: 10.1039/C6RA27138C.

The authors regret errors in Fig. 4, ​,7,7, and 9 in the previously published article. The corrections for the errors in the article are described as follows:Open in a separate windowFig. 4Kubelka–Munk absorbance spectra and band gaps (insets) of the pure InVO₄ (a) and 1.0 mol% Cu-doped InVO₄ (b) samples.Open in a separate windowFig. 7Schematic of the charge migration and separation on Cu-doped InVO₄.(1) The diffuse reflectance spectra of pure InVO₄ and 1.0 mol% Cu-doped InVO₄ are shown in Fig. 4. The absorption margin of 1.0 mol% Cu-doped InVO₄ was shifted to a longer wavelength, indicating a decrease in the band gap with respect to pure InVO₄. The absorption margins of the pure InVO₄ and 1.0 mol% Cu-doped InVO₄ samples were 505 nm and 510 nm, corresponding to band gaps of 2.51 eV and 2.45 eV, respectively (Fig. 4a and b).(2) The band edge positions of the conduction band (CB) and the valence band (VB) of InVO₄ can be calculated by the following equation: E⁰_CB = χ − E^C − 0.5E_g,¹ where χ is the electronegativity of the semiconductor, E^C is the energy of free electrons on the hydrogen scale of 4.5 eV, E_g is the band gap of InVO₄, and the χ value of InVO₄ is 5.74 eV.² The E_g value of InVO₄ evaluated from the UV-vis DRS analysis was about 2.51 eV. The valence band energy (E_VB) can be calculated by the following equation:³E_VB = E_CB + E_g, where E_CB is the conduction band energy. Based on the equation above, the calculated CB and VB edge potentials of InVO₄ were −0.02 eV and 2.49 eV, respectively. Now, we are in a position to discuss the photocatalytic mechanism of Cu-doped InVO₄ for MB degradation (Fig. 7). In the photocatalysis process, when the absorbed photon energy (hν) equals or exceeds the band gap, the Cu-doped InVO₄ generates electron–hole (e⁻/h⁺) pairs. In that case, the generated electrons from the valence band can be transferred to the conduction band of InVO₄. Since the CB edge potential of InVO₄ (−0.02 eV) is higher than the standard redox potential, E⁰(O₂/O₂˙⁻) = −0.33 V vs. NHE at pH 7, this suggests that the electrons in the CB of InVO₄ cannot reduce O₂ to the superoxide radical ion (O₂˙⁻). In addition, the VB of InVO₄ (2.49 eV) is higher than the standard redox potential, E⁰(OH⁻/OH˙) = 1.99 V vs. NHE at pH 7. This indicates that the photogenerated holes in the valence band of InVO₄ can oxidize the hydroxyl ion (OH⁻) or water (H₂O) to form the hydroxyl radical (OH˙).(3) Due to the contradiction between the scavenging test and the proposed photocatalytic mechanism, Fig. 9 was removed from the original article.The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers.     

Hydrothermal synthesis of MoS2 nanosheet loaded TiO2 nanoarrays for enhanced visible light photocatalytic applications

A molybdenum disulfide (MoS₂) nanosheet-decorated titanium dioxide (TiO₂) NRA heterojunction composite was fabricated successfully through a two-step hydrothermal approach. Microstructures and optical properties of specimens were characterized by field-emission scanning electron microscopy, X-ray diffractometry, X-ray photoelectron spectroscopy, and ultraviolet-visible spectroscopy. The gaps of the TiO₂ nanorods have been filled with tiny MoS₂ nanosheets, which can increase the surface area of MoS₂/TiO₂ NRA composite thin films. In addition, the photocatalytic activity of the thin films were measured and discussed in greater detail. The appropriate hydrothermal reaction temperature of MoS₂ is important for the growth of perfect MoS₂/TiO₂ NRA composites with significantly enhanced photocatalytic performance. The photodegradation rate and k value of MoS₂-220/TiO₂ are 86% and 0.0105 min⁻¹, respectively, which are much larger than those of blank TiO₂. The enhanced photocatalytic performance could be attributed to the higher visible light absorption and the reduced recombination rate of photogenerated electron–hole pairs.

A molybdenum disulfide (MoS₂) nanosheet-decorated titanium dioxide (TiO₂) NRA heterojunction composite was fabricated successfully through a two-step hydrothermal approach.     

Facile synthesis of an urchin-like Sb2S3 nanostructure with high photocatalytic activity

Herein, an urchin-like Sb₂S₃ nanostructure has been synthesized without a surfactant via a wet chemical method. The crystal structure, morphology, composition and optical properties were characterized using XRD, TEM, SEM, EDS, Raman spectroscopy, and diffuse reflectance absorption spectroscopy. The factors, including the reaction time, temperature, and ratio of the raw materials, influencing the evolution of the urchin-like morphology have been discussed, and a plausible formation mechanism for the urchin-like Sb₂S₃ has been proposed. The urchin-like Sb₂S₃ micro/nanostructure exhibits high catalytic performance towards the degradation of MB under visible light irradiation. The photodegradation ratio of MB is up to 99.32% under visible light irradiation of 130 min. Our synthesis method will be extended to prepare other photocatalysts.

Urchin-like Sb₂S₃ has been successfully synthesized without a surfactant using a wet chemical method. The as-prepared unique nanostructure provides a high specific surface area, leading to superior catalytic performance under visible light irradiation.

In recent years, nanomaterials with controllable size and novel morphologies have been extensively studied due to their unique physical and chemical properties.^1–5 For instance, AgBr nanoplates,⁶ AgCl octahedrons⁷ and NaTi₂(PO₄)₃ nanocubes⁸ show unique photocatalytic activities and electrochemical performances. Hierarchical flower-like SnO₂ nanospheres⁹ or TiO₂ nanorod arrays^10,43 exhibit highly efficient gas sensing and photoelectrochemical properties.As an important V–VI compound, antimony sulfide (Sb₂S₃) is considered as a promising material for energy conversion due to its suitable band gap (1.5–2.2 eV), which covers the range of the solar spectrum.^11–13 To the best of our knowledge, Sb₂S₃ nanomaterials with different morphologies have been mainly synthesized using various surfactants.¹⁴ Surfactants can regulate the morphology and structure of the nanoparticles effectively by parceling on the surface of the particles through the coordination or charge effect.¹⁵ By adding surfactants such as cetyltrimethylammonium bromide (CTAB),¹⁶ polyethylene glycol (PEG),¹⁷ dodecyltrimethylammonium bromide (DTAB)¹⁸ and polyvinylpyrrolidone (PVP),^19–21 some nanostructures including straw-tied-like, nanorod^22,23, nanosheet,²⁴ nanotube, dandelion-like, double cauliflower-like,²⁵ bar,²⁶ dumbbell-like, and nanowire bundle structures have been successfully prepared, which show potential applications in photocatalysis and energy storage areas. However, how to effectively synthesize Sb₂S₃ crystals and control their morphology via a simple method is still challenging for materials scientists. Herein, we report a simple wet chemical method to synthesize an urchin-like Sb₂S₃ nanostructure without any surfactant. Moreover, we have examined the photocatalytic activity of Sb₂S₃ by the degradation of MB under simulated visible light irradiation. Our study presents an Sb₂S₃ nanostructure with good application in the visible-light photocatalytic field.The morphology and size of the products were revealed by the SEM and TEM images. Fig. 1a shows the SEM image of the urchins-like Sb₂S₃ prepared under refluxing conditions at 160 °C for 5 h. The as-prepared Sb₂S₃ products mainly consist of the uniform urchin-like structure. The magnified SEM image shows that the urchin-like structure consists of nanorods stretching radially from the same central point (Fig. 1b). The TEM image further confirms that the urchin-like Sb₂S₃ is made up of many individual nanorods with lengths about 10 μm and diameters of 100 nm (Fig. 1b and c). The measured spacing of the crystallographic planes is 0.309 nm, which is consistent with the (320) plane lattice distance of orthorhombic Sb₂S₃ (Fig. 1d).Open in a separate windowFig. 1(a) SEM, (b and c) TEM and (d) HRTEM images, (e) XRD pattern and (f) EDS spectrum of urchin-like Sb₂S₃.The XRD pattern of the obtained sample is shown in Fig. 1e. All the diffraction peaks in the XRD pattern can be readily indexed to orthorhombic Sb₂S₃ (JCPDS no. 42-1393) with the calculated lattice parameters of a = 1.120 nm, b = 1.128 nm and c = 0.383 nm. No characteristic peaks for impurities are observed. The fact that the reflection peaks of Sb₂S₃ are strong and sharp indicates that Sb₂S₃ is highly crystalline (Fig. 1e). The EDS spectrum reveals that the as-prepared products consist of S and Sb elements, and the observed C and Cu peaks are due to the carbon-coated Cu grid²⁷ (Fig. 1f). Furthermore, the elemental distribution ratio of S and Sb in the compound was found to be about 3 : 2 through the quantification calculation of the EDS peaks, which was consistent with the chemical formula of antimony sulfide.²⁸The effects of the reaction time, reaction temperature and the ratio of the raw materials on the as-obtained products were carefully studied to investigate the formation of the urchin-like morphology. Fig. 2 reveals the SEM images of the as-obtained samples prepared at different reaction times. Initially, no product was formed. When the reaction time was prolonged to 2 h, amorphous antimony sulfide was formed (Fig. 2a). After 3 h, single units with slight splitting were observed (Fig. 2b). Upon increasing the reaction time, uniform urchin-like Sb₂S₃ was obtained. When the reaction time was further increased to 6 h, the urchin-like structure was transformed into a rod-flower structure in which the thorns of the urchin-like structure were thicker (Fig. 2c). As shown in Fig. 2d and e, after 9 h, the rod-flower structure began to rupture and finally converted into irregular nanorods with lengths of about 15 μm, as shown in Fig. 2f.Open in a separate windowFig. 2SEM images of the Sb₂S₃ prepared at 160 °C for different times: (a) 2 h, (b) 3 h, (c) 6 h, (d) 9 h, (e) 12 h, and (f) 15 h.The reaction temperature also has a significant effect on the morphologies of the final products. As shown in Fig. 3a, amorphous nanoparticles with an irregular shape were formed at 140 °C. When the temperature was increased to 150 °C, a simple splitting phenomenon appeared. Upon further increasing the temperature, the urchin-like micro/nanostructure was formed. A further increase in the reaction temperature led to the formation of rod flowers. When the reaction temperature was 180 °C, some rod-like structures appeared.Open in a separate windowFig. 3SEM images of Sb₂S₃ prepared for 5 h at different reaction temperatures: (a) 140 °C, (b) 150 °C, (c) 170 °C and (d) 180 °C.We examined the effect of the ratio of the raw materials on the product. Only rod particles were observed at a ratio of S/Sb = 1 : 1 (Fig. 4a). When the ratio was increased to 1 : 3, the urchin shapes were observed. A further increase in the concentration of the sulfur source led to the appearance of nest structures. Irregular spherical particles were finally generated when the ratio of the raw materials was 1 : 7.Open in a separate windowFig. 4SEM images of Sb₂S₃ prepared with different ratios of S and Sb: (a) S/Sb = 1 : 1, (b) S/Sb = 1 : 3, (c) S/Sb = 1 : 5, and (d) S/Sb = 1 : 7.Based on the experimental results, a plausible reaction for the synthesis of the Sb₂S₃ crystals can be interpreted as follows:CH₃CSNH₂ + 2OH⁻ → S²⁻ + CH₃COO⁻ + NH⁴⁺1[Sb₂(C₄H₄O₆)₂]²⁻ → 2Sb³⁺ + 2(C₄H₄O₆)⁴⁻22Sb³⁺ + 3S²⁻ → Sb₂S₃↓3According to the abovementioned experimental results, we speculated the formation mechanism of the urchin-like Sb₂S₃ structure. Sb₂S₃ is a highly anisotropic semiconducting material with infinite ribbon-like (Sb₄S₆) polymers and layers in its orthorhombic crystal structure.^29,30 As already reported in the literature, Sb₂S₃ tends to easily form one-dimensional nanorods along the c-axis due to intermolecular attraction between the antimony and sulfur atoms.^31–34 Because of the fast and anisotropic crystal growth, many newborn clusters agglomerate together to deposit on a particular particle face, causing crystal splitting when the solution is in the excess saturation state.^35,36 Then, each of the nanorods starts to grow into urchin-like crystals. This is similar to the chain-like crystalline structure of Bi₂S₃; this further ascertains that Sb₂S₃ has a strong splitting ability.^37,38 Our research suggests that the degree of splitting is increased when the reaction time is prolonged. In the subsequent stage, the nanorods are detached from the urchin-like structures; this results in well-dispersed nanorods due to the instability of the surface energy.³⁹ The whole process of this morphological evolution is shown schematically in Fig. 5. The amorphous nanoparticles of Sb₂S₃ appeared with no splitting. Upon increasing the reaction time, the Sb₂S₃ nanostructures change from small sheaves with simple splitting to urchin-like structures.Open in a separate windowFig. 5A schematic of the formation of the urchin-like Sb₂S₃ structure.The fact that the optical properties of the as-prepared Sb₂S₃ are determined using the absorption spectrum (Fig. 6a) provides a simple and effective method to estimate the band gap of the urchin-like Sb₂S₃.^40,41 The band gap value of 1.64 eV determined by other researchers is quite comparable to the values reported in the bibliographical information.⁴² Furthermore, it can be seen that optical absorption occurs in nearly all the visible light region; this suggests that the as-synthesized Sb₂S₃ can be stimulated by visible light. Raman spectrum of the urchin-like Sb₂S₃ is shown in Fig. 6b. The appearance of sharp peaks at 147, 198, 257, 305, and 452 cm⁻¹ suggests the formation of a highly crystalline product, which is consistent with the XRD results.⁴³ Due to suitable band gap of urchin-like Sb₂S₃, the photocatalytic activity of urchin-like Sb₂S₃ was assessed by depositing an organic dye (MB) in an aqueous solution under visible light irradiation. The concentration of MB dye was monitored at 665 nm using an UV/vis spectrophotometer. From the blank experiment (Fig. S2^†), we can see a slight drop in the curve due to self-degradation of MB dye under visible light irradiation. Therefore, we can conclude that the dye is almost photo-stable under these conditions. It can be clearly observed from Fig. 6c that the organic dye is slightly degraded by Sb₂S₃ in the dark. According to Fig. 6d, the organic dye could be degraded by only 23.1% using H₂O₂, whereas the degradation efficiency for MB dye was 99.34% in the presence of Sb₂S₃ and H₂O₂ after 130 min; this indicated that the degradation of the organic dye was mainly attributed to the excellent photocatalytic activity of Sb₂S₃. The photoluminescence spectra of the as-prepared urchin-like Sb₂S₃ shows a low signal, suggesting the good charge separation properties of our samples (Fig. S1a^†). Fig. S1b^† shows the I–T curves of the FTO/Sb₂S₃ photoelectrode, of which the photocurrent intensity is 36.057 μA cm⁻² at a potential of 0 V versus Ag/AgCl, and this fast photocurrent response is consistent with the PL results. Fig. 6e shows the photocatalytic degradation of an aqueous solution of MB at different concentrations by urchin-like Sb₂S₃. However, with an increase in the concentration of MB, the degradation efficiency is reduced. Furthermore, the cycling performance of urchin-like Sb₂S₃ was measured using the same photodegradation process. The photocatalyst was obtained by centrifugation and washed with deionized water after each cycle. The degradation ratio decreased slightly after reuse for 5 times; the slight decay in the photodegradation activity was partially ascribed to the inevitable loss of the photocatalyst during the washing and centrifugation process; this suggested that Sb₂S₃ exhibited prominent photocatalytic stability (Fig. 6f).Open in a separate windowFig. 6(a) The diffuse reflectance absorption spectrum of the as-prepared Sb₂S₃ sample (the inset presents the corresponding plots of (αhυ)²versus photon energy). (b) The room-temperature Raman spectrum. (c) The degradation curve for MB in the dark. (d) The degradation curves for MB using the different catalyst systems (e) the degradation curves at different MB concentrations. (f) The cycling runs for the degradation of MB.The promising photocatalytic activity of Sb₂S₃ can be mainly attributed to its relatively narrow band gap (1.64 eV), making it a perfect photocatalyst to efficiently absorb and utilize visible-light energy. As is known, the urchin-like nanostructure has been extensively investigated due to its potential applications in many areas such as in varistors, electronic devices, UV-absorbers, and catalysis.^47,48 This kind of nanostructure has a high specific surface area, which endows it with a large contact area with the dye and superior light harvesting efficiency in the field of photocatalysis.⁴⁹ Moreover, the single crystalline nanorod-assembled urchin-like nanostructure is favorable for fast electron transfer and thus facilitates electron and hole separation.^46,50,51 In particular, when urchin-like Sb₂S₃ is irradiated by visible light of energy greater than its band gap, electron–hole pairs will be generated and partially separated. The electrons and holes react with the adsorbed surface substances, such as O₂ and OH⁻, to form the reactive species ·O²⁻, ·OH, which are the major oxidative species in the decomposition of organic pollutants. Then, the oxidative species degrade the organic pollutant into small molecules such as CO₂ and H₂O.^44,45p-Benzoquinone (BQ) and isopropyl alcohol (IPA) were used as additive agents to trap the active species ·O₂⁻ and ·OH, respectively. Fig. S2^† shows the degradation curves for MB after the addition of the different capture agents. It can be seen that IPA has a significant inhibitory effect on the degradation of MB, whereas the effect of BQ is less; this indicates that ·OH plays a major role in the photocatalytic process.The degradation of the organic dye was accomplished via a series of parallel and consecutive redox reactions as show in eqn (2.1)–(2.5).Sb₂S₃ + hν → Sb₂S₃ (h⁺_VB + e⁻_CB)2.1O₂ + e⁻_CB → ·O⁻₂2.2H₂O → H⁺ + OH⁻2.3OH⁻ + h⁺_VB → ·OH2.4MB + ·OH + ·O²⁻ → CO₂ + H₂O + …2.5In summary, an urchin-like Sb₂S₃ nanostructure was successfully prepared without surfactants using a wet chemical method. The corresponding crystal splitting formation mechanism of urchin-like Sb₂S₃ was tentatively suggested. The narrow band gap of the urchin-like Sb₂S₃ was evaluated to be 1.64 eV, which was close to the best photoelectric conversion value reported to date. In addition, urchin-like Sb₂S₃ exhibited excellent photocatalytic performance; the degradation efficiency for the organic dye was 99.34% after exposure to visible-light irradiation for 130 min. The high photocatalytic activity of Sb₂S₃ was mostly due to its narrow band gap and wide absorption range of visible light. Our investigation demonstrates that Sb₂S₃ with urchin-like nanostructures has great potential to be applied in the degradation of organic contaminants.     

Facile synthesis of few-layer MoS2 in MgAl-LDH layers for enhanced visible-light photocatalytic activity

A new photocatalyst, few-layer MoS₂ grown in MgAl-LDH interlayers (MoS₂/MgAl-LDH), was prepared by a facile two-step hydrothermal synthesis. The structural and photocatalytic properties of the obtained material were characterized by several techniques including powder X-ray diffraction (XRD), Raman spectroscopy, field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), photoluminescence spectroscopy (PL) and UV-vis absorption spectroscopy. The MoS₂/MgAl-LDH composite showed excellent photocatalytic performance for methyl orange (MO) degradation at low concentrations (50 mg L⁻¹ and 100 mg L⁻¹). Furthermore, even for a MO solution concentration as high as 200 mg L⁻¹, this composite also presented high degradation efficiency (>84%) and mineralization efficiency (>73%) at 120 min. The results show that the MoS₂/MgAl-LDH composite has great potential for application in wastewater treatment.

Few-layer MoS₂ was successfully grown in MgAl-LDH layers, utilizing the “space-confining” effect. The composite completed degraded 50 mg L⁻¹ and 100 mg L⁻¹ methyl orange (MO) solutions in 45 min and 105 min, respectively.     

Visible light photocatalytic one pot synthesis of Z-arylvinyl halides from E-arylvinyl acids with N-halosuccinimide

An efficient visible light photocatalytic strategy to synthesize thermodynamically less stable Z-arylvinyl halides (with up to >99/1 Z/E ratio and 86% yield) was developed. The reaction combined base-mediated halodecarboxylation of E-arylvinyl acids with N-halosuccinimide and visible light Ir-photocatalyzed isomerization of E-arylvinyl halides in a one pot sequential catalytic process.

An efficient visible light photocatalytic strategy to synthesize Z-arylvinyl halides from E-arylvinyl acids using N-halosuccinimide through a sequential halodecarboxylation/photoisomerization with up to >99/1 Z/E ratio and 86% yield under mild reaction conditions.

Visible light photocatalysis has received considerable attention in recent years owing to the mild reaction conditions, green and sustainable chemistry features, and high atom-economy.¹ As reported in the literature, two different activation modes are commonly used. Most of the photochemical reactions proceed through a single-electron transfer (SET) process from the excited photosensitizers to the organic substrates or reagents. The other activation mode is an energy transfer (EnT) process in which no charge separation is involved in the whole process. This EnT activation pathway mainly depends on the triplet-state energies of the photosensitizers and the organic substrates. Synthetically useful visible light-induced organic transformation reactions through the EnT process have been successfully developed in the past decades.^1n,2The synthesis of multisubstituted alkenes is an important reaction because of their versatile utility as synthetic building blocks for organic synthesis and as structural elements contributing to the significant biological properties of natural products and pharmaceuticals.³ Unlike E-alkenes, the strategies for synthesis of thermodynamically less stable Z-alkenes are not readily accessible.⁴ Hammond and Arai developed pioneering photochemical E → Z isomerisations of stilbenes and styrenes and delineated the reaction mechanisms.⁵ Inspired by these mechanistic studies, visible light induced E → Z isomerization has attracted great interest. In 2014, Weaver and co-workers reported Ir(ppy)₃ catalyzed E to Z isomerization of allylamines proceeding via an EnT mechanism.⁶ In 2015, the Gilmour group developed photoisomerization of activated alkenes using (−)-riboflavin as an EnT photocatalyst.⁷ Furthermore, Gilmour and co-workers have reported photoisomerization of styrenyl boron species and selective isomerization of β-borylacrylates.⁸ In 2020, the same group reported a synthetic procedure for E → Z isomerization of β-borylacrylates via EnT using thioxanthone as the sensitizer eliminating the need of an aryl unit for alkene isomerization, and the inert aryl rings were replaced by a traceless BPin handle.⁹Arylvinyl halides are versatile synthetic intermediates for organic synthesis. In particular, transition metal-catalyzed cross couplings of vinyl halides with organometallics, such as, organo boronic and organozinc reagents, are efficient methods for synthesis of multisubstituted alkenes.¹⁰ However, synthesis of the thermodynamically less stable Z-isomer still poses a great challenge. In 2019, Yu''s group demonstrated a synthetically useful E → Z photocatalytic isomerization of styrenyl halides (Scheme 1).¹¹ On the other hand, decarboxylation of α,β-unsaturated arylvinyl acids accompanied by simultaneous replacement by halogen is a useful reaction for the synthesis of styrenyl halides.¹² Considering the importance of Z-vinyl halides in the synthesis of multisubstituted alkenes, we hypothesize that it would be interesting to combine the halodecarboxylation of α,β-unsaturated arylvinyl acids and photoisomerization of E-arylvinylhalides in a one pot sequential catalytic process. Herein, we report a novel method to synthesize Z-arylvinyl halides by visible light Ir-photocatalyzed reaction of E-arylvinyl acids with N-halosuccinimide.Open in a separate windowScheme 1Photocatalytic synthesis of multisubstituted alkenes.Our group has synthesized a series of new fluorescent quinolizinium compounds from quinolines and alkyne substrates.¹³ Due to the high tunability and high excited state reduction potentials of the fluorescent quinolizinium compounds, we proposed that the quinolizinium compounds could be used as photocatalysts for the synthesis of Z-arylvinyl halides from α,β-unsaturated arylvinyl acids.With this idea in mind, we started the initial investigation by treatment of (2E)-3-phenyl-2-butenoic acid (1a) with 2 equiv. of N-bromosuccinimide (NBS) in the presence of 5 mol% of photocatalyst 3a in CH₃CN at room temperature under 30 W blue LEDs irradiation. 36% NMR yield of the desired product (Z/E)-(1-bromoprop-1-en-2-yl)benzene (Z/E-2a) was obtained with modest selectivity (Z/E = 44/56). Next, we optimized the reaction conditions by varying the additives. Adding K₂CO₃ and TBAI, E-2a was obtained only (entries 2–3, EntryPhotocatalyst (PC)AdditiveYield^b Z/E^c13a—4544/5623a1 eq. K₂CO₃880/10033a1 eq. TBAI750/10043a1 eq. CH₃CO₂H4356/4453a2 eq. CH₃CO₂H3577/2363a3 eq. CH₃CO₂H5866/3473a2 eq. PhCO₂H2199/183a0.3 eq. PhCO₂H3294/693b0.3 eq. PhCO₂H2986/14103c0.3 eq. PhCO₂H2291/9113d0.3 eq. PhCO₂H3884/16123e0.3 eq. PhCO₂H2488/12133f0.3 eq. PhCO₂H3394/6143g0.3 eq. PhCO₂H3586/14153h0.3 eq. PhCO₂H4969/31163i0.3 eq. PhCO₂H6360/40 Open in a separate window^aReaction conditions: treatment of E-1a (0.2 mmol), NBS (0.4 mmol) and photocatalyst (5 mol%) in 2 mL of CH₃CN under N₂ and blue LEDs light for 17 hours at room temperature.^bYield was determined by ¹H NMR using dibromomethane as internal standard.^cThe Z/E ratio was determined by ¹H NMR spectroscopy.Then, we screened the reaction conditions with metal photocatalyst Ir(ppy)₃. Styrenyl hailde 2a was obtained in 48% NMR yield in a Z/E ratio (52 : 48) (entry 1, EntryPhotocatalyst (PC)AdditiveYield^b Z/E^c1^dIr(ppy)₃0.3 eq PhCO₂H4852/482Ir(ppy)₃0.3 eq PhCO₂H0—3Ir(ppy)₃—0—4Ir(ppy)₃0.3 eq. K₂CO₃3161/395Ir(ppy)₃2 eq. K₂CO₃6097/36Ir(ppy)₃2.5 eq. K₂CO₃5695/57Ir(ppy)₃3 eq. K₂CO₃4996/48Ir(ppy)₃2 eq. Na₂CO₃5795/59Ir(ppy)₃2 eq. Cs₂CO₃5494/610Ir(ppy)₃2 eq. K₃PO₄6489/1111Ir(ppy)₃2 eq. tBuOK3892/812Ir(ppy)₃2 eq. DBU4794/613Ir(ppy)₃2 eq. Et₃N967/3314Ir(Fppy)₃2 eq. K₂CO₃5689/1115Ir(diFppy)₃2 eq. K₂CO₃7379/2116Mes-Acr-BF₄2 eq. K₂CO₃3010/9017Ru(bpy)₃(PF₆)₂2 eq. K₂CO₃645/9518Ru(bpy)₃Cl₂2 eq. K₂CO₃480/10019^eIr(ppy)₃2 eq. K₂CO₃740/10020—2 eq. K₂CO₃544/96Open in a separate window^aReaction conditions: treatment of E-1a (0.2 mmol), NBS (0.4 mmol) and photocatalyst (2 mol%) in 2 mL of MeOH under N₂ and blue LEDs light for 17 hours at room temperature.^bYield was determined by ¹H NMR using dibromomethane as internal standard.^cThe Z/E ratio was determined by ¹H NMR spectroscopy.^dThe reaction solvent was CH₃CN.^eNo light irradiation.After optimizing the reaction conditions, we next sought to explore the scope of the reaction. The results summarized in Open in a separate window^aReactions were performed with 0.2 mmol substrate at room temperature in MeOH (2.0 mL) using 2 mol% fac-Ir(ppy)₃ under 30 W blue LEDs irradiation. Z/E ratios were determined by ¹H NMR spectroscopy. Isolated yields.^b5.0 mmol scale.^c5 mol% fac-Ir(ppy)₃.^d1 mol% fac-Ir(ppy)₃.To gain mechanistic insight on this reaction, the reaction progress was monitored under the optimized reaction conditions (Scheme 2). Complete halodecarboxylation of E-1c was observed in 1 hour to give E-2c, which suggests that the isomerisation is the rate-determining step. Some product Z-2c was obtained after 2 hours. Almost complete E → Z isomerization was observed over the course of 16 hours.Open in a separate windowScheme 2Reaction progress monitoring of E-1c.At last, we performed two Pd-catalyzed coupling reactions with styrenyl bromide Z-2j to further illustrate the synthetic utility of this cascade reaction (Scheme 3). When 4-methoxyphenylboronic acid was treated with bromide Z-2j using Pd(PtBu₃)₂ as catalyst, Suzuki–Miyaura cross coupling reaction¹⁴ successfully afforded trisubstituted alkene Z-4 (Z/E = 98/2) in 78% yield. Moreover, Sonogashira coupling reaction¹⁵ with 1-ethynyl-4-methylbenzene gave enyne Z-5 (Z/E = 98/2) in 87% yield.Open in a separate windowScheme 3Pd-catalyzed coupling reactions of styrenyl bromide Z-2j.     

Facile one-pot synthesis of Mg-doped g-C3N4 for photocatalytic reduction of CO2

Graphitic carbon nitride (g-C₃N₄) has attracted wide attention due to its potential in solving energy and environmental issues. However, rapid charge recombination and a narrow visible light absorption region limit its performance. In our study, Mg-doped g-C₃N₄ was synthesized through a facile one-pot strategy for CO₂ reduction. After Mg doping, the light utilization efficiency and photo-induced electron–hole pair separation efficiency of the catalysts were improved, which could be due to the narrower band gap and introduced midgap states. The highest amounts of CO and CH₄ were obtained on Mg-CN-4% under ultraviolet light illumination, which were about 5.1 and 3.8 times that of pristine g-C₃N₄, respectively; the yield of CO and CH₄ reached 12.97 and 7.62 μmol g⁻¹ under visible light irradiation. Our work may provide new insight for designing advanced photocatalysts in energy conversion applications.

Graphitic carbon nitride (g-C₃N₄) has attracted wide attention due to its potential in solving energy and environmental issues.     

Vortex fluidic mediated synthesis of polysulfone

Polysulfone (PSF) was prepared under high shear in a vortex fluidic device (VFD) operating in confined mode, and its properties compared with that prepared using batch processing. This involved reacting the pre-prepared disodium salt of bisphenol A (BPA) with a 4,4′-dihalodiphenylsulfone under anhydrous conditions. Scanning electron microscopy (SEM) established that in the thin film microfluidic platform, the PSF particles are sheet-like, for short reaction times, and fibrous for long reaction times, in contrast to spherical like particles for the polymer prepared using the conventional batch synthesis. The operating parameters of the VFD (rotational speed of the glass tube, its tilt angle and temperature) were systematically varied for establishing their effect on the molecular weight (M_w), glass transition temperature (T_g) and decomposition temperature, featuring gel permeation chromatography (GPC), differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA) respectively. The optimal VFD prepared PSF was obtained at 6000 rpm rotational speed, 45° tilt angle and 160 °C, for 1 h of processing with M_w ∼10 000 g mol⁻¹, T_g ∼158 °C and decomposition temperature ∼530 °C, which is comparable to the conventionally prepared PSF.

Polysulfone (PSF) was prepared under high shear in a vortex fluidic device (VFD) operating in confined mode. This involved reacting the pre-prepared disodium salt of bisphenol A (BPA) with a 4,4′-dihalodiphenylsulfone under anhydrous conditions.     

Correction: Synthesis of Bi2WO6/Na-bentonite composites for photocatalytic oxidation of arsenic(iii) under simulated sunlight

Correction for ‘Synthesis of Bi₂WO₆/Na-bentonite composites for photocatalytic oxidation of arsenic(iii) under simulated sunlight’ by Quancheng Yang et al., RSC Adv., 2019, 9, 29689–29698.

Ref. 28 in the published article was incorrect, with an incorrect page range provided. The correct version is shown as ref. 1 below.The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers.     

Correction: Cu(ii)/Ni(ii)–organic frameworks constructed from the homometallic clusters by 5-(2-carboxyphenoxy)isophthalic acid and N-ligand: synthesis,structures and visible light-driven photocatalytic properties

Correction for ‘Cu(ii)/Ni(ii)–organic frameworks constructed from the homometallic clusters by 5-(2-carboxyphenoxy)isophthalic acid and N-ligand: synthesis, structures and visible light-driven photocatalytic properties’ by Qi-Wei Xu et al., RSC Adv., 2019, 9, 16305–16312.

In the Acknowledgements section, a funder, Laboratory Open Project Fund of Capital Normal University (LIP18009S047) was omitted.The revised acknowledgements should read:The authors are grateful to the Key Project of Science and Technology plan of Beijing Education Commission (KZ201910028038), the National Natural Science Foundation of China (21471104) and Laboratory Open Project Fund of Capital Normal University (LIP18009S047).The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers.     

Base mediated spirocyclization of quinazoline: one-step synthesis of spiro-isoindolinone dihydroquinazolinones

A novel approach for the spiro-isoindolinone dihydroquinazolinones has been demonstrated from 2-aminobenzamide and 2-cyanomethyl benzoate in the presence of KHMDS as a base to get moderate yields. The reaction has been screened in various bases followed by solvents and a gram scale reaction has also been executed under the given conditions. Based on the controlled experiments a plausible reaction mechanism has been proposed. Further the substrate scope of this reaction has also been studied.

A novel approach for the spiro-isoindolinone dihydroquinazolinones has been demonstrated from 2-aminobenzamide and 2-cyanomethyl benzoate in the presence of KHMDS as a base to get moderate yields.

Because of their strong potent biologically activity, heterocyclic compounds have been a constant source of inspiration for the invention of new drugs especially for pharmaceutical and agro chemical industries.¹ Indeed, investigation of novel methods for the synthesis of various natural products and heterocycles has always been a challenging task in modern organic chemistry. Amid all, spiro based scaffolds have been found to be very interesting because of their structural diversity. In spite of their intrinsic structures and immense biological activity there is a tremendous demand for the chemistry of spiro-isoindolinone dihydroquinazolinones.² Indeed, nitrogen containing heterocyclic compounds like spiro-oxindole, spiro-isoindoline, spiro-isoindolinone are playing a significant role in medicinal chemistry and synthetic transformations.³ Moreover these compounds present in many natural products as a core unit like Lennoxamine, Zopiclone, Taliscanine and Pazinaclone (Fig. 1). In addition, many unnatural spiro-isoindolinones show significant biological activities acting as anti HIV-1, antiviral, antileukemic, anesthetic and antihypertensive agents.^4,5 Notably, the spiro-isoindolinone dihydroquinazolinone unit has been found to be a combination of two potent pharmacophore units of dihydroquinazolinone and spiro-isoindolinone. Inspite of their remarkable biological activity afore mentioned, various methods have been developed for their synthesis like lithiation approaches, base mediated protocols, Diels–Alder and Wittig reactions, electrophilic and radical cyclization, metal-catalysed reactions and various electrochemical procedures.⁶Open in a separate windowFig. 1Some biologically active spiro-isoindolinone and quinazolinone units.Previously, a number of metal catalyzed reactions have also been reported for the spiroannulations.⁷ Among all, Nishimura et al. developed an Ir(i) catalyzed [3 + 2] annulation of benzosultam and N-acylketimines with 1,3-dienes via C–H activation for the synthesis of aminocyclopentene derivatives. Further, Xingwei Li et al. developed a Rh(iii)-catalysed [3 + 2] annulation of cyclic N-sulfonyl or N-acyl ketimines with activated alkenes for the preparation of various spirocyclic compounds.⁸ Recently Yangmin Ma et al. developed a one pot nano cerium oxide catalyzed synthesis of spiro-oxindole dihydroquinazolinone derivatives (Scheme 1).^5c However, development of these type of novel compounds is always challenging and more attractive. Indeed, to the best of our knowledge there are no reports for the synthesis of spiro-isoindolinone dihydroquinazolinones. This led us to give more attention to study these compounds.Open in a separate windowScheme 1Different strategies for the synthesis of quinazolinone units.In continuation of our earlier efforts⁹ for the synthesis of various dihydroquinazolinones, herein we would like to report KHMDS mediated synthesis of novel spiro-isoindolinone dihydroquinazolinones. We envisioned the retro synthetic pathway for these compounds, as depicted in Scheme 2. Accordingly these compounds could be synthesised from 2-aminobenzamide and methyl-2-cyanobenzoate or ethyl-2-cyanobenzoate.Open in a separate windowScheme 2Retro synthetic approach for the synthesis of quinazolinone unit.Indeed, in order to understand the reaction conditions, we have commenced the reaction by taking 2-amino-N-hexyl-benzamide (2) and methyl-2-cyanobenzoate (3) as a model substrates. However, in the initial phase of reaction optimisation, we have screened the reaction in different bases (Fig. 2) and to our delight amongst all the bases KHMDS, LiHMDS and NaHMDS were amenable to get moderate yields. However the reaction had not progressed at low temperatures (5 °C) and could improve the yield at room temperature. Moreover the reaction underwent complete conversion with 1.5 equivalents of base. Further, the reaction was also executed with ethyl-2-cyanobenzoate and could replicate the same yield. Incontinuation, the reaction was futile when the reaction was carried out in DIPEA, DBU, K₂CO₃ and Cs₂CO₃. Subsequently, the reaction in NaOMe and ^tBuOK produced exclusively the hydrolysis product (4) of methyl-2-cyanobenzoate (Open in a separate windowFig. 2Base screening in 1,4-dioxane.Optimisation of the base-mediated spiroannulation^a

Correction: Solvent-controlled synthesis of multicolor photoluminescent carbon dots for bioimaging

Correction for ‘Solvent-controlled synthesis of multicolor photoluminescent carbon dots for bioimaging’ by Yang Yan et al., RSC Adv., 2019, 9, 24057–24065.

The authors regret that the contributions of the authors were not correctly indicated in the original article. Yang Yan should be designated as the sole first author, and therefore the footnote stating “The two authors contributed equally” was in error. The correct author list is as shown above.The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers.